Adjustable doctor blade assembly for yankee dryers and like machines



J. B. SISSON 3,378,876 DOCTOR BLADE ASSEMBLY FOR YANKEE RYERS AND LIKE MACHINES 2 Sheets-Sheet 1 April 23, 1968 ADJUSTABLE D Filed Aug. 25, 1965 INVENTOR.

James B. Sjsson BY W c .wm

ATTORNEYS Aprll 23, 1968 a. SISSON 3,378,876

ADJUSTABLE DO R BLADE ASSEMBLY FOR YANKEE DRYERS AND LIKE MACHINES Filed Aug. 23, 1965 2 Sheets-Sheet 2 Fig.3 22 Fig l Q L9 &

I A 1 28 I w 48 INVEN'TOR.

' James B Sisson $0 WCLUUt +h/leew'wST 21mg 50 ATTORNEYJ United States Patent M 3,378,876 ADJUSTABLE DOCTOR BLADE ASSEMBLY FOR YANKEE DRYERS AND LIKE MACHINES James B. Sisson, Hamilton, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Aug. 23, 1965, Ser. No. 481,686 5 Claims. (Cl. 256.51)

ABSTRACT OF THE DISCLOSURE An adjustable doctor blade assembly useful in supporting a flexible doctor blade with its edge in operative contact with a Yankee dryer or other drum surface. In the adjustable doctor blade assembly, the flexible doctor blade edge is urged against a drum surface by a plurality of backup bar segments. Each backup bar segment is adjustably mounted and fixedly positionable at varying distances in relation to the flexible doctor blade edge. The scraping action along the length of the flexible doctor blade edge against the drum surface can be adjusted to achieve an advantageous profiled scraping or creping action by positioning the individual backup bar segments. The advantageous profiled scraping action can be achieved and maintained despite minor grinding irregularities in the flexible doctor blade edge and the associated drum surface.

The present invention relates to doctor blade assemblies for rotary drum dryers, or like devices. More particularly, the invention relates to creping doctor blade assemblies for use in connection with the rotary drum dryers used in papermaking.

Specifically the invention consists of an adjustable doctor blade assembly, having a supporting bar for a flexible doctor blade and a plurality of backup bar segments, each of which is adjustably mounted in opposing direction to the supporting bar and fixedly positionable in relation to the operative edge of the flexible doctor blade, for use in connection with the Yankee dryers used in the production of light weight papers, and like rotary dryer drums.

Inasmuch as the most careful machining of doctor blade edges and dryer drum faces does not completely and initially match a doctor blade edge with the drum surface which it scrapes, it has in the past been the practice to mount and wear in the doctor blade edge on the dryer drum surface itself. Careful machining, mounting and wearing in can result in matching the doctor blade edge to a dryer drum surface. Even these methods, however, fail to take into account variations in the reaction of the material being scraped or creped from the dryer drum. For example, minor variations in the thickness, dryness and contact of a paper sheet across a Yankee dryer face can cause irregular creping action across the paper sheet. Also, the action of a freshly machined or ground doctor blade results in a finer, more uniform creping action than that obtained with a doctor blade which has been matched to a dryer surface by wearing in.

In view of the difficulties encountered in achieving an even creping action across the width of a Yankee dryer drum, various means for varying the loading pressure transversely along the length of a doctor blade have been developed. For example, U.S. Pat. 3,040,222, issued to Lyle S. Overton on June 26, 1962, discloses the use in a doctor blade assembly of a plurality of pneumatically loaded fingers supra-mounted to a plate backing up a doctor blade to vary the loading pressure applied along the length of the doctor blade. Also, U.S. Pat. 2,330,889, issued to Norval J. Holcomb on Oct. 5, 1943, discloses the use of a plurality of presser fingers which are adapted 3,378,876 Patented Apr. 23, 1968 to press against a doctor blade with a predetermined force along its length. In addition, U.S. Pat. 1,762,157, issued to Samuel J. Campbell on June 10, 1930, discloses a creping plate having mounted thereon a series of plates which are spring loaded to yield With variations in the thickness of the material undergoing creping.

In contrast to these doctor blade assemblies, the present invention provides for an adjustable doctoring, scraping or creping action along the length of a flexible doctor blade which is capable of adjustment for cross-machine variations in the thickness, dryness, or tackiness of the maten'al coming into contact with. the operative edge of the flexible doctor blade, as well. as machining variations in the flexible doctor blade edge and the dryer drum surface. The adjustable creping action is accomplished by varying the distance of individual backup bar segments from the operative edge of the flexible doctor blade along its length, as the creping action indicates, and thereafter fixing their position until further adjustment is made desirable by any change in creping action. The use of a plurality of backup bar segments as a means of multiposition transverse pressure adjustment provides for a stable, more vibrationless creping action and in addition provides a construction which is capable of adjustment While the flexible doctor blade edge is in operative position against the surface of a roll. It is noted that the plurality of backup bar segments in a particular application of the instant adjustable doctor blade assembly will include suflicient of such segments to provide a desirable number of adjustment points without being so numerous that unstable or impractical operation results.

The flexible doctor blade is disposed in a transverse channel formed between a support means comprising a bar, which can have an inset for slidably receiving the flexible doctor blade and partially defining the transverse channel, and a plurality of backup bar segments. The supporting bar inset can directly engage the inoperative edge of the flexible doctor blade or alternatively, the flexible doctor blade can be spaced outwardly from the supporting bar inset by a spacer bar. The flexible doctor blade can also be given a measure of stiffness by providing a flexible backup strip for the flexible doctor blade. The flexible backup strip can be a separate element, mounted in loose contact with the flexible doctor blade, or it can be machined as a part of the flexible doctor blade itself.

In one embodiment of the invention, the individual backup bar segments are adjusted with respect to the operative edge of the flexible doctor blade by means of bolts which are threadedly engaged in the nether side of the backup bar segments and whose heads contact a shoulder of the support bar.

In another embodiment, the individual backup bar segments are adjusted with respect to the operative edge of the flexible doctor blade by means of a plurality of threaded rod elements which are threadedly engaged with opposing screw directionality into both the individual backup bar segments and a shoulder provided on the support bar. In this embodiment the threaded rod elements are provided with a flatted section, which may be square or hexagonal, disposed between the backup bar segments and the support bar shoulder for convenience in adjustment.

The adjustable doctor blade assembly is conveniently mounted in operative position by means of projecting pivots provided at each end of its support bar, and the entire assembly can be rotated to position the operative edge of the flexible doctor blade in contact with a dryer drum surface with which the assembly is used. This rotation can be accomplished by loading means which can be comprised of a loading lever actuated by an air cylinder. The contact angle of the flexible doctor blade with a dryer drum surface can be adjusted by altering the position of the projecting pivots. More conveniently, but to a lesser degree, the contact angle can be adjusted by altering the distance of the operative edge of the flexible doctor blade from the pivotal axis of the adjustable doctor blade assembly.

Accordingly, it is an object of the present invention to provide an adjustable doctor blade assembly wherein a flexible doctor blade is provided with a plurality of individually adjustable and fixedly positionable backup bar segments by means of which the scraping action of the flexible doctor blade can be adjusted along its operative edge.

Another object is to provide an adjustable doctor bar assembly wherein the scraping action along the operative edge of a flexible doctor blade is adjusted by means of a plurality of backup bar segments, each of which are adjustably mounted and fixedly positionable in relation to the operative edge of the flexible doctor blade.

Still another object is to provide a preferred adjustable doctor blade assembly wherein the scraping action of a flexible doctor blade is adjusted along its length 'by means of a plurality of backup bar segments, each of which are adjustably mounted and fixedly positionable in relation to the operative edge of the flexible doctor blade and wherein the individual backup bar segments are adjusted by means of threaded elements disposed between the individual backup bar segments and support means for the flexible doctor blade.

Other objects and advantages of the invention will become apparent as the description proceeds in accordance with the drawings in which like numbers refer to like elements and in which:

FIGURE 1 is a perspective view of a preferred embodiment of the adjustable doctor blade assembly of the present invention mounted in operative relation to the surface of a drying drum.

FIGURE 2 is a partial vertical elevation of an adjustable doctor blade assembly corresponding to that shown in FIGURE 1.

FIGURE 3 is a side sectional view of the partial adjustable doctor blade assembly shown in FIGURE 2 as taken along line 3-3.

FIGURES 4, 5, 6, 7 and 8 are side sectional views of additional embodiments of the present invention illustrated in the manner of FIGURE 3.

Referring now to the drawings, a roll surface is shown in operative contact with a flexible doctor blade 22 mounted in an adjustable doctor blade assembly 24 according to the invention. The adjustable doctor blade assembly 24 of the invention is adaptable to a variety of roll scraping operations ranging from operation with a chilled roll to operation with high temperature drying rolls; it is particularly useful in connection with the creping treatments commonly given to toweling and tissue papers during their manufacture.

A supporting means comprising a bar 26, having projecting pivots 28 at its opposite ends for mounting purposes and a loading lever 30 attached to its nether side, is provided for the flexible doctor blade 22.

Referring now to FIGURES 1 and 2, the adjustable doctor blade assembly 24 is mounted on a pair of projecting pivots 28 and includes a bar support means 26 for the flexible doctor blade 22. The bar support means 26 defines a transverse channel 32 of substantially rectangular cross-sectional configuration into which a spacer bar 34, the flexible doctor blade 22 and a flexible backup strip 36 are slidably inserted. The transverse channel 32 is further defined by a plurality of backup bar segments 38, some of which are shown in adjusted positions with respect to the operative edge of flexible doctor blade 22 and which are attached to bar support means 26 by a plurality of bolts 40. The bolts 40 pass through slotted holes 42 in the backup bar segments 38 and through 4 holes 44 (shown in FIGURES 3, 4 and 8) in the spacer bar 34 and are threadedly engaged in the bar support means 26. The backup bar segments 38 are also provided with a plurality of bolts 46 threadedly engaged in the nether side thereof and abutting on a shoulder 48 provided on bar support means 26.

The contact angle a which the flexible doctor blade 22 makes with roll surface 20 is seen to be widely adjustable by varying the mounting position of bar support means 26 on its projecting pivots 28 with relation to the roll surface 20. More convenient, but lesser, adjustment of the contact angle on may be had by varying the width of flexible doctor bar 22 and the width of spacer bar 34, thereby varying the distance of the operative edge of flexible doctor blade 22 from the rotational axis of projecting pivots 28. It is seen that with a specific positioning of the projecting pivots 28 in relation to roll surface 20 that decreasing the width of either or both of flexible doctor blade 22 and spacer bar 34 will result in an increased contact angle a as the adjustable doctor blade assembly 24 is rotated into operative position about the center line of projecting pivots 28 by a force acting on lever 30 through pivotally connected arm 50. An increase in width in either or both of flexible doctor blade 22 and spacer bar 34 will result in a decreased contact angle a.

The adjustable doctor blade assembly 24 can be urged into operative position by a variety of means including air cylinders, steam cylinders and mechanical weighting means operating either directly upon lever 30 or upon lever 30 through pivotally connected arm 50. The adjustable doctor blade assembly 24 .may also be mounted in operative position by a variety of convenient and conventional mechanical means other than the pivotal mounting on projecting pivots 28.

The overall loading applied to the operative edge of flexible doctor blade 22 is governed by the force applied to rotate the adjustable doctor blade assembly 24 around the projecting pivots 28 through the lever 30. As implied heretofore, however, the method of mounting the adjustable doctor blade assembly 24 and applying an overall loading to the operative edge of flexible doctor blade 22 is not a part of the present invention, and any mounting and loading means known to those skilled in the art can be used to accomplish these functions.

The multiposition transverse pressure adjustment means which are the concern of the present invention are comprised in part of the plurality of backup bar segments 38. In operation each of the backup bar segments 38 are adjustable and fixedly positionable in distance from the operative edge of flexible doctor blade 22. The distance between each of the backup bar segments 38 and the operative edge of flexible doctor blade 22 can be adjusted to vary the moment arm-spring tension of flexible doctor blade 22 above each backup bar segment 38. Adjustment of each backup bar segment 38 is accomplished by loosening the bolts 40 passing through it and adjusting its posi tion by rotating the bolts 46 threadedly engaged therein inwardly or outwardly until the desired distance and relationship with the operative edge of flexible doctor blade 22 above is achieved. The foregoing adjustment can be accomplished while the adjustable doctor blade assembly 24 is mounted in operating position adjacent the roll surface 20 and the operative edge of flexible doctor blade 22 is doctoring, scraping or creping product from roll surface 20. The desired position of each of the backup bar segments 38 is easily judged by noting the creping action of the operative edge of flexible doctor blade 22 thereabove. For example, a loose or sagging stripe in a creped paper product issuing from the flexible doctor blade at a certain cross-machine position along its length can often be corrected by positioning the associated backup bar segment 38 farther from the operative edge of flexible doctor blade 22. As another example, the presence of holes at a certain cross-machine position in the creped paper product, caused by doctor blade pickout, can often be corrected by positioning the associated backup bar segment 38 closer to the operative edge of flexible doctor blade 22 to exert more scraping pressure at that position. When the doctoring action of flexible doctor blade 22 has been adjusted or profiled to result in even or other desired scraping or creping action, the bolts 40 passing therethrough are tightened. The operation is thereafter continued until some new cross-machine direction variation in product dryness, thickness, bond with roll surface, stiffness, etc. makes repositioning one or more of the backup bar segments 38, with respect to the operative edge of the flexible doctor blade 22, necessary or desirable to maintain product quality.

Flexible doctor blade 22 can be constructed of steel, bronze, fiber, plastic or other material known to those skilled in the art and suitable for the doctoring operation contemplated. Likewise, the present invention is not restricted to specific materials of construction in the remainder of the components of the adjustable doctor blade assembly 24, and while steel, stainless steel, bronze and similar metals are more common in usage, any material contemplated by those skilled in the art for a specific doctoring operation can be utilized.

Referring now to FIG. 3, a side sectional view of the partial adjustable doctor blade assembly 24 shown in FIG- URE 2 as taken along line '3'-3, there is pnovided a bar support means 26 having projecting pivot 28 and loading lever 30, and a spacer bar 34 with belt 40 passing through hole 44. There is further provided a flexible doctor blade 22, a flexible backup strip 36, and adjustable backup bar segment 38 with a slotted hole 42 therein, through which bolt 40, threadedly engaged in bar support means 26, is passed. Bolt '46 is threadedly engaged in the nether side of backup bar segment 38 and rests on the shoulder 48 provided on bar support means 26. FIGURE 3 shows the components depicted in FIGURES l and 2 in like cooperating position and depicts in greater detail their method of cooperation, showing in some instances, as do FIGURES 4, 5, 6, 7 and 8, only one of elements existing in plurality in adjustable doctor blade assembly 24.

Referring now to FIGURE 4, there is shown an embodiment of the present adjustable doctor blade assembly 24 wherein bar support means 26 is not provided with shoulder 48, and adjustment of the individual backup bar segments 38 is accomplished by tapping them or otherwise moving them into the desired position relative to the operative edge of flexible doctor blade 22 prior to tightening bolts 40.

Referring to. FIGURE 5, there is shown an adjustable doctor blade assembly similar to that depicted in FIG- URE 3, with the exception that bolt 40 passes through hole 44a and 44b in the flexible doctor blade 22 and flexible backup strip 36 instead of through hole 44 in spacer bar 34. The widths of both flexible doctor blade 22 and flexible backup strip 36 are increased to make up for the space not occupied by spacer bar 34.

Referring to FIGURE 6, there is shown an adjustable doctor blade assembly 24 similar to that depicted in FIG- URE 3, with the exception that no flexible backup strip 36 is provided and the plurality of bolts 46 are exchanged for a plurality of threaded rod elements 46a which are thre a'dedly engaged in both backup bar segments 38 and bar support means 26 by threads of opposing directionality and are provided with a flatted section 52 therebetween for the engagement of an open-end wrench or other adjustment means. The backup bar segments 38 are provided with a face relief 38a to insure desirable pressure contact of the backup bar segments 38 with the flexible doctor blade 22. This construction of backup bar segments 38 with face relief 38a can also be employed to advantage in other embodiments of the invention.

Referring to FIGURE 7, there is shown an adjustable doctor blade assembly 24 wherein the transverse channel 32 in which the flexible doctor blade 22 and the flexible backup strip 36 are slidably inserted is above the position of threaded engagement of bolts 40 with bar support means 26. This embodiment of the invention may be used with a spacer bar 34 inserted into transverse channel 32 beneath flexible doctor blade 22 and flexible backup strip 36, and has the advantage that the aforementioned elements may be exchanged for elements having different widths and thicknesses without removing bolts 40 and backup bar segments 38, as in the embodiments wherein bolts 40 pass through holes in same.

Referring to FIGURE 8, there is illustrated a preferred adjustable doctor blade assembly 24 wherein a second spacer bar 34a is used to gain the advantage of additional spacing flexibility and convenience in replacing spacing surfaces which may become worn or corroded in operation. The heads of bolts 40 are also recessed in this embodiment of the invention to avoid the possibility of production interruptions caused by snagging product on exposed bolt heads.

It will thus be seen that there has been provided an adjustable doctor blade assembly which has multiposition transverse pressure adjustment means which are capable of conve1ting an overall loading on the operative edge of a flexible doctor blade to a desired creping or scraping action at a multiplicity of points along the operative edge of said blade. It is also seen that the contact angle with which the operative edge of the flexible doctor blade engages a roll surface may be easily varied by varying the width of the flexible doctor blade and/ or spacer bar associated therewith when the adjustable doctor blade assembly is mounted on pivots projecting from its opposite ends. Even greater contact angle adjustment can be achieved by adjusting the mounting position of the projecting pivots about whose axis the adjustable doctor blade assembly rotates. It is further seen that in embodiments of the invention wherein bolting means do not pass through flexible doctor blade, flexible backup strip and/ or spacer bar elements, that these elements can be changed with rapidity to facilitate flexible doctor blade replacement and angle adjustment. The possibility of manufacturing the flexible doctor blade from a variety of plastic, fiber metal materials and the remainder of the components of the adjustable doctor blade assembly from suitable materials known to those skilled in the art, makes the ready assembly of an adjustable doctor blade assembly suitable for a great variety of doctoring operations a reality.

Although the invention has been set forth herein and described with respect to certain specific principles and details thereof, it will be understood by those skilled in the art that these may be varied without departing from the spirit and scope of the invention as set forth in the hereunto appended claims.

Having thus described the invention, what is claimed is:

1. In an adjustable doctor blade assembly comprising, in combination, a flexible doctor blade and support means for said blade, the improvement which comprises providing a plurality of backup bar segments for said blade, each of which backup bar segments is adjustably mounted in opposing direction to said support means and fixedly positionable at varying distances in relation to the operative edge of said blade.

2. In an adjustable doctor blade assembly comprising, in combination, a flexible doctor blade and support means for said blade, the improvement which comprises providing a plurality of backup bar segments for said blade, each of which backup bar segments is adjustably mounted in opposing direction to said support means and fixedly positionable at varying distances in relation to the operative edge of said blade, and a plurality of bolts passing through slotted holes in said bar segments and threadedly engaged in said support means for securing said bar segments to said support means.

3. In an adjustable doctor blade assembly comprising, in combination, a flexible doctor blade, support means for said blade and a spacer bar for spacing said blade outwardly from said support means, the improvement Which comprises providing a plurality of backup bar segments adjustably mounted in opposing direction to said support means and fixedly positionable at varying distances in relation to the operative edge of said blade and a plurality of bolts passing through both slotted holes in said bar segments and holes in said spacer bar and threadedly engaged in said support means for securing said bar segments to said support means.

4. In an adjustable doctor blade assembly comprising, in combination, a flexible doctor blade and support means for said blade, the improvement which comprises providing a plurality of backup bar segments for said blade, each of which backup bar segments is adjustably mounted in opposing direction to said support means and fixedly positionable at varying distances in relation to the operative edge of said blade and forms together with said support means a transverse channel into which said blade is slidably inserted, a plurality of bolts passing through slotted holes in said bar segments and threadedly engaged in said support means for securing said bar segments to said support means, and a plurality of bolts threadedly engaged in said bar segments and abutting said support means for positioning said bar segments relative to the operative edge of said blade.

5. In an adjustable doctor blade assembly comprising, in combination, a flexible doctor blade, a flexible backup strip for said blade, support means for said blade and backup strip and a spacer bar for spacing said blade outwardly from said support means, the improvement which comprises providing a plurality of backup bar segments, each of which backup bar segments is adjustably mounted in opposing direction to said support means and fixedly positionable at varying distances in relation to the operative edge of said blade, forming together with said support means a channel into which said blade, backup strip and spacer bar are slidably inserted, a plurality of bolts passing through slotted holes in said bar segments and threadedly engaged in said support means for securing said bar segments to said support means, and a plurality of rod elements threadedly engaged in both said bar segments and said support means for positioning said bar segments relative to the operative edge of said blade.

References Cited UNITED STATES PATENTS 1,311,431 7/1919 Adt 15256.51X 2,145,550 1/1939 Loose 15 256.5 2,273,021 2/1942 Cox 15 256.51 2,477,339 7/1949 Ljungguist 15 256.51 3,061,867 11/1962 Hill 15 256.51 3,113,890 12/1963 Johnson etal ll8--l26 3,164,492 1/1965 Schmittetal. 15256.51X 3,309,992 3/1967 Motter 118261 X CHARLES A. WILLMUTH, Primary Examiner.

L. G. MACHLIN, Assistant Examiner. 

